1. Field of the Invention
The present invention relates to a pattern exposure technique for forming a circumferential or radial pattern on a disk-shaped recording medium of a magnetic disk device by utilizing a pattern forming technique which is used in the field of manufacturing a wiring board or semiconductor package. More particularly, the present invention relates to a variable rectangle-type electron beam exposure apparatus in which exposure is conducted with a rectangular beam. The present invention also relates to a pattern forming method for exposing and forming a pattern with the variable rectangle-type electron beam exposure apparatus described above.
2. Description of the Related Art
In order to provide magnetic disk devices having a large memory capacity, the recording density of a disk-shaped recording medium has been increased every year. Therefore, in the case where servo information is written on the disk-shaped recording medium so that a magnetic head for reading and writing the signal information on the disk-shaped recording medium can be positioned with respect to the disk-shaped recording medium, it has become difficult to form a servo information pattern with an exclusively used device while the mechanical accuracy is kept high. In order to reduce a manufacturing cost of the disk-shaped recording medium on which the servo information pattern is written, it is necessary to make the servo information for positioning easily and accurately.
In order to satisfy the requirement described above, the following method has been considered. By the electron beam exposure technique used in the manufacturing process of a semiconductor device, a master board of the positioning information pattern is first made, and then the servo information is made as a whole when the positioning information pattern is transferred to the disk-shaped recording medium. However, according to the method of the prior art, in order to form a highly accurate pattern, it is necessary to use the electron beam exposure technique. When a commonly used point beam type electron beam exposing apparatus, by which an arbitrary figure can be drawn, is used, in order to make a servo information pattern on the entire face of one piece of the disk-shaped recording medium, the diameter of which is 5 to 10 cm, by applying this technique, an extremely long exposure time is required for making the servo information pattern. Therefore, this method can not be put into practical use.
FIG. 14 is a view showing a pattern exposure and formation method conducted by the point beam type electron beam exposing machine. In FIG. 14, with respect to the pattern to be made or the area of figure A, the exposure area of point beam B is very small. Therefore, for example, in the case where exposure is conducted while point beam B is gradually shifted in order in the direction of the arrow, in order to expose the entire region of figure A, an extremely long exposure time is required as described above.
In order to solve the above problems caused in the case where the point beam type electron beam exposing machine is used, if a variable rectangle-type electron beam exposing machine is used, a reduction of the exposure time will come to be possible. Further, when an arrangement and shape of the rectangle are changed appropriately, a very fine exposure can be conducted so as to form a fine line pattern of an arbitrary angle.
FIG. 15 is a view showing a pattern exposure and formation method conducted by a variable rectangle-type electron beam exposing machine. In FIG. 15, with respect to the area of the pattern or figure A to be formed, the region area of rectangular beam B is comparatively large. Therefore, when exposure is conducted while rectangular beam B is gradually shifted, exposure can be accomplished in a short period of time. According to the shape of the pattern or figure A to be formed, the shape and the size of rectangular beam B may be appropriately adjusted.
However, in the case of the variable rectangle-type electron beam exposing machine shown in FIG. 15, the following problems may be encountered. In the case where an inclined angle of the pattern or figure A to be made and an angle of rectangular beam B are different from each other, for example, in the case where the pattern or figure A to be made is extended by an inclination angle of about 45° with respect to the side of exposure region B of the rectangular beam, an edge portion of the pattern or figure A does not agree with the angle of the rectangular exposure region B. Therefore, the area of rectangular beam B must be reduced to as small as possible. After all, in the same manner as the case of the point beam type electron beam exposure, a long exposure time is required.
In this connection, the related prior art is disclosed in the official gazette of Japanese Unexamined Patent Publication (Kokai) No. 9-826630, which will be described below. The variable formation electron beam drawing apparatus disclosed in JP-A 9-82630 has the target of meeting the following demands. The degree of freedom of designing the device pattern is increased; the drawing of an inclined pattern having an arbitrary angle is demanded; and an inclined pattern having an arbitrary angle is drawn with high accuracy and high throughput without using a transfer mask. In order to meet the above demands, in the variable formation electron beam drawing apparatus having two rectangular apertures for forming a beam, a third aperture, in which a pivotal slit capable of being rotated about an optical axis by a highly accurate motor, is provided under a rectangular aperture for forming a beam, and an arbitrary parallelogram beam is formed by rotating the third aperture.
The variable formation electron beam drawing apparatus described in JP-A 9-82630 is preferably used for the exposure of an arbitrary parallelogram beam. However, with respect to a predetermined fine line pattern having an arbitrary angle, it is impossible to conduct a highly fine exposure in the pattern region.
In the case where the above conventional point beam type electron beam exposing machine is used, it takes an extremely long time for the exposing machine to expose and form the servo information pattern on the entire face of a piece of disk-shaped recording medium. Therefore, it is difficult to put the conventional point beam type electron beam exposing machine into practical use.
In the case where the conventional variable rectangle-type electron beam exposing machine is used, it is possible to conduct exposure in a short period of time, however, in order to conduct exposure with high accuracy, it is necessary to appropriately change the arrangement and shape of the rectangle. However, especially when the pattern angle and the rectangular beam angle are different from each other at the edge portion of the pattern, it is impossible to conduct exposure with high accuracy. Alternatively, when the rectangular beam size is reduced, the exposure time is prolonged.
The variable formation electron beam drawing apparatus described in JP-A 9-82630 is preferably used for the exposure of forming an arbitrary parallelogram beam. However, this variable formation electron beam drawing apparatus is not suitable for the highly accurate exposure of a predetermined fine line pattern having an arbitrary angle in the pattern region.
Therefore, it is an object of the present invention to provide a variable rectangle-type electron beam exposure apparatus and a pattern exposure-formation method capable of conducting a highly fine exposure of a predetermined fine line pattern having an arbitrary angle in the pattern region when several types of the rectangular beam angles are prepared.